Social-emotional competence, coping, and vulnerability are assessed in a longitudinal study of young children with an affectively ill parent. The sample consists of 48 predominantly middle-class families. Children of mothers with unipolar depression (current major, past major, or past minor) and normal mothers are seen at two and at five years of age. They are observed in a laboratory setting in interaction with their mothers, adult strangers, and familiar playmates. The affective environment is varied experimentally to assess children's social-emotional responses. An earlier investigation using similar procedures to study two-year-old children with a bipolar parent indicated significant problems in the quality of interpersonal relations, ability to empathize with playmates, and in resolution of hostile impulses. Analysis are underway to determine (a) whether similar social-emotional problems characterize children with parents with unipolar depression and (b) whether the severity and chronicity of parental illness influence the child's functioning. Comparisons are made of the children's behavior at two and five years in order to explore processes associated with continuities and discontinuities in social-emotional patterns of coping in children with an affectively ill parent.